Continuously engaged tangential driving tool

ABSTRACT

Wrench for continuous driving engagement with a rotatively driven element such as a screw, bolt or nut, which is particularly suitable for use where the ends of the driven element are not accessible and in applications where space for manipulation of the tool is limited such as in spinal fusion surgery. The wrench has a peripheral driving element which can be engaged from the side with the driven element, and an articulating handle which enables the wrench to rotate the driven element through a substantial angle with only a few degrees of handle movement.

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation-in-part of Ser. No. 297,762, filed Jan. 17, 1989.

BACKGROUND

1. Field of Invention

This invention pertains generally to wrenches and other tools and, moreparticularly, to apparatus for applying a driving torque to a drivenelement.

2. Description of Prior Art

It is common practice to use rotatively driven mechanical devices todraw two objects together or to push two objects apart. Common examplesof devices for drawing objects together are bolts and nuts, and anexample of a device for pushing objects apart is a jack screw. Suchdevices commonly have some feature that makes it possible to rotate themwith a tool. A nut or the head of a bolt, for example, might have ahexagonal shape, a square shape, or another shape suitable forengagement by a wrench, and the head of a bolt or screw may be providedwith a slot or other suitable opening for engagement by a screwdriver.

It is frequently desirable to be able to engage these devices with atool to provide continuous rotation of the device without having todisengage and re-engage the tool for each successive increment ofrotation. This continuous turning capability is particularly useful insituations where time is critical or space is limited.

Heretofore, some tools have been provided for continuous matingengagement with bolts, nuts and the like to apply a driving torque tothem. Common examples of such tools include socket wrenches withratcheting handles and certain box wrenches with ratcheting mechanisms.However, the tools heretofore provided of this type have one commondrawback that severely limits their use. They require that the end ofthe nut, bolt or other driven device be unobstructed and accessiblebecause the tool must be placed on or over the end of the device toapply the torquing force.

Many times the ends of the driven devices are covered, obstructed orotherwise not accessible, in which case continuously engaged torquingtools cannot be used, and some other tool such as an open end wrench ora pair of pliars must be employed. These other tools do not allowcontinuous turning of the driven device, but instead require that thetool be disengaged and re-engaged for successive increments of rotation.The process of repeatedly repositioning the tool and making only alimited degree of rotation with each positioning is inefficient and timeconsuming. It is especially undesirable and difficult when working insmall, confined spaces like those that often occur when performingsurgical procedures.

One surgical procedure where space for manipulation of a wrench islimited is back fusion surgery. In back fusion surgery, a spinal boneseparating device is often used to separate the spinal bones inpreparation for the bone fusion. Such a bone separation device consistsof two threaded hooks that engage the bones to be separated. These hooksmount on oppositely threaded sections of a jack screw which is rotatedby means of a hex shaped nut affixed to the screw between the oppositelythreaded sections. Access to the nut from the ends of the screw isblocked by the hooks so that a continuously engaged torquing tool suchas a socket wrench cannot be utilized to turn the screw. An open endedbox wrench is the tool which is currently used in this situation. Withthis tool, the limited space available and the limited visibility insuch surgery, the task of separating the bones is extremely difficultand time consuming for doctors to perform.

OBJECTS AND SUMMARY OF THE INVENTION

It is in general an object of the invention to provide a new andimproved tool for continuous driving engagement with a rotatively drivenelement such as a screw, bolt or nut.

Another object of the invention is to provide a tool of the abovecharacter which overcomes the limitations and disadvantages of toolsheretofore provided.

Another object of the invention is to provide a tool of the abovecharacter which can be utilized in situations where the ends of thedriven element are not accessible and/or space for manipulation of thetool is limited.

Another object of the invention is to provide a tool of the abovecharacter which is particularly suitable for use in spinal fusionsurgery.

These and other objects are achieved in accordance with the invention byproviding a wrench having a peripheral driving element adapted to beengaged from the side with a driven element, a relatively short headwhich carries the driving element and is adapted to impart a drivingtorque to the driving element when swung back and forth about the axisof the driven element, means for holding the driving element inperipheral driving engagement with the driven element, an elongatedhandle for swinging the head back and forth about the axis of the drivenelement, and means pivotally connecting the elongated handle to therelatively short head for movement about an axis parallel to the axis ofthe driven element to permit articulation between the handle and thehead as the head is swung back and forth to produce the tangentialdriving force.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of one embodiment of a continuously engagedtorquing tool according to the invention in driving engagement with abone separator of the type employed in spinal fusion surgery.

FIG. 2 is an exploded view of the torquing tool in the embodiment ofFIG. 1.

FIG. 3 is an exploded view of the bone separator in the embodiment ofFIG. 1.

FIG. 4 is an elevational view illustrating the bone separator in theembodiment of FIG. 1 in connection with the spinal bones.

FIG. 5 is an isometric view of another embodiment of a continuouslyengaged torquing tool according to the invention in driving engagementwith a bone separator of the type employed in spinal fusion surgery.

FIG. 6 is an exploded view of the torquing tool in the embodiment ofFIG. 5.

FIG. 7 is an exploded view of the bone separator in the embodiment ofFIG. 5.

FIG. 8 is an isometric view of another embodiment of a continuouslyengaged torquing tool according to the invention.

FIG. 9a and 9b are operational views illustrating the use of theembodiment of FIG. 8.

In FIG. 1, a rotational driving tool or wrench 16 is shown in drivingengagement with a bone separator 17.

The tool has a pair of side plates or cover plates 20, 22, typically 5inches in length, which are secured together in spaced parallel relationby screws 24, 26 and nuts 28, 30 and form a handle by which the tool canbe manipulated. A torquing drive gear 32, typically a 0.5 inch diameterby 0.16 inch thick spur gear with 18 teeth, is rotatively mounted onscrew 26, with a bushing 34 between the gear and the screw, and spacers36, 38 between the bushing and the side plates. A flat spring 40,typically made of spring steel, is attached to a mounting block 42 byscrews 44, and the mounting block is attached to side plate 20 by screws46 and nuts 48. One end of the flat spring projects about 0.1 inch fromthe mounting block and engages the teeth of drive gear 32 to serve as apawl which permits the gear to rotate in one direction only. A spacer 50on screw 24 provides separation between the upper portions of coverplates 20, 22 when screw 24 is tightened.

Aligned notches 21, 23 are provided in the lower portions of side plates20, 22 between drive gear 32 and the ends of the plates. The notchesopen through the lower ends of the plates and extend in an upwarddirection to a point just below the teeth of the drive gear. The lowerend portions of the side plates thus have a fork-like configurationwhich is adapted to engage a driven element such as the jack screw ofthe bone separator from the side, with the screw being rotativelyreceived in the notches and the teeth of gear 32 in tangential drivingengagement with the driven element.

As illustrated in FIG. 3, the bone separator has a pair of jaws in theform of oppositely facing semicircular hooks 52, 54 threadedly mountedon oppositely threaded sections 56, 58 of a jack screw 59 for movementtoward and away from each other upon rotation of the screw. In thisparticular embodiment, screw section 56 has a left hand thread andsection 58 has a right hand thread. A drive gear 60 is affixed to thescrew between the two threaded sections and adapted for drivingengagement by the drive gear 32 of the driving tool. A suitable gear formeshing engagement with a drive gear having the specifications givenabove is an 18 tooth spur gear having a diameter of 0.5 inch and athickness or width of 0.16 inch.

Operation and use of the driving tool in the installation of a spinalbone separator, e.g. during spinal fusion surgery, is as follows. Hooks52, 54 are initially positioned close together on jack screw 59 andhooked between the two spinal bones 53, 55 to be separated, asillustrated in FIG. 4. The driving tool is then brought into engagementwith the jack screw, with pawl spring 40 facing away from the directionthe screw is to be rotated to separate the hooks. The fork-like endportions of side plates 20, 22 fit over the screw from the side so thatthe screw is rotatively received in notches 21, 23 and the teeth ofdrive gear 32 are held securely in meshing engagement with the teeth ofgear 60 for tangentially driving the same.

With the drive gears engaged, the tool can be swung back and forth aboutthe axis of the screw and will drive the screw with a ratcheting action.When the tool is swung away from the direction the pawl spring faces,the end of the spring engages the teeth of drive gear 32, preventingthat gear from turning, which causes the driving force of the tool to betransmitted tangentially to the drive gear 60 on the screw. When thetool is swung in the direction the pawl spring faces, drive gear 32turns freely, and no force is transmitted to the screw. Thus, a back andforth movement of the tool drives the screw in a given direction withthe tool in continuous engagement with the screw.

The direction in which the screw is rotated can be reversed bydisengaging the driving tool from the screw, rotating the tool 180°about its longitudinal axis so the pawl spring faces in the oppositedirection, and reengaging the tool with the screw. Thus, the tool can beused to turn the screw in the bone separating device to either increaseor decrease the separation of the bones.

In spinal fusion surgery, the bones to be separated are located deep inthe back where space and visibility are both quite limited. Theseconditions make the installation and adjustment of a bone separatorquite difficult, and the problem is further complicated by the fact thatthe access to the ends of the screw which operates the separator isobstructed by the jaws or hooks of the device and by nearby bones andtissue. Even under these conditions, driving tool 16 can be engagedrelatively easily with the operating screw of the bone separator. Thetool can turn the screw in a mimimum of space since it only requiresenough movement to advance the drive gear one step of the ratchetingmechanism at a time. With a handle having a length on the order of fiveinches, a back and forth movement of an inch or two at the outer end ofthe handle is generally sufficient.

Once engaged, the tool remains in continuous engagement with the screwuntil the adjustment is completed. This greatly simplifies the task ofthe doctor in installing the separator during surgery.

FIGS. 5-7 illustrate an embodiment of the tool which is particularlysuitable for use in situations where space is so limited that it mightnot be possible to swing a handle back and forth a sufficient distanceto actuate a ratchet.

In this embodiment, the tool 61 has an elongated handle 62 with anenlarged upper portion 63, and a crossbar 64 extending laterally fromthe upper portion. A drive gear 76 is affixed to a shaft 66 which isreceived in an axial bore 65 in the lower portion of the handle, with asetscrew 72 securing the shaft to the handle. Drive gear 76 is a helicalgear of suitable pitch and diameter, and in one suitable embodiment ithas a pitch diameter of 0.33 inch.

A generally rectangular block 68 having a vertically extending bore 69of slightly greater diameter than shaft 66 is rotatively mounted on theshaft between drive gear 76 and the lower end of handle 62, with theshaft passing through the bore in the block. Side plates 70 are affixedto opposite sides of the block, with a pair of aligned notches 71opening through the lower ends of the plates to form a fork-likestructure for engaging a driven element to hold drive gear 76 intangential driving engagement with that element.

The bone separator 73 which is illustrated in FIGS. 5-7 is similar tothe separator 17 illustrated in

FIGS. 1-4, and like reference numerals designate corresponding elementsin the two embodiments. In separator 73, however, drive gear 78 is ahelical gear which is adapted for driving engagement by the helicaldrive gear 76 of tool 61.

Operation and use of the driving tool 61 with the bone separator 73 isas follows. The jaws or hooks of the separator are positioned betweenthe bones to be separated, as in the previous embodiment. The tool isbrought into driving engagement with the separator screw by moving thetool toward the screw until the screw is received in the notches 71 inthe fork-like side plates 70, and the drive gear 76 is in meshingengagement with gear 78. With the gears meshed, handle 62 is rotatedabout its axis to turn drive gear 76 and thus turn the separator screwabout its axis to move the separator jaws or hooks. The handle can beturned in either direction, depending upon the direction in which thejaws or hooks are to be moved.

The rotary driving tool 61 of FIGS. 5-7 can be utilized in many of thesame applications as the ratcheting tool 16 of FIGS. 1-4, and it canalso be utilized in applications where there might not be enough room toswing the handle of the ratcheting tool.

In spinal fusion surgery, driving tool 61 can be easily engaged with theadjusting screw of the bone separator even though space and visibilitymay both be severely limited. The tool can be used where space isminimal since the handle 62 extends completely out of the surgical workarea and can be easily rotated without hitting any bones or tissue. Likethe embodiment of FIGS. 1-4, the tool remains in continuous engagementwith the driven element and greatly simplifies the task of the doctor ininstalling bone separating devices during back fusion surgery eventhough space is limited and the ends of the screw are inaccessablebecause of the hooks or jaws of the device as well as nearby bones andtissue.

The embodiment of the tool illustrated in FIG. 8 has an articulatinghandle 81, which enables the tool to turn a driven element through agreater angle of rotation in certain applications than a tool with arigid handle. The tool has a relatively short head 82 to which thehandle is connected by a pin 83 for movement about an axis 84 parallelto the axis of the driven element. The outer portion of the handle has aknurled section 86 to facilitate gripping.

A drive gear 87 is rotatively mounted in the head of the tool forrotation about an axis parallel to pivot axis 84 and the axis of thedriven element. A pawl spring 89 engages the teeth of the drive gear andpermits it to rotate in one direction only. An arrow 90 is engraved orstamped on the upper end of handle 81 to indicate the direction ofhandle rotation in which the pawl spring provides a positive drivingconnection between the head and the drive gear. The distal end of thehead is bifurcated and has a pair of hook-like fingers or jaws 91 withlaterally facing openings 92 for receiving the shaft of the drivenelement and holding drive gear 87 in tangential driving engagement withthe driven element. This tool can be used for adjusting bone separatorsof the type shown in FIGS. 1-4, as well as in other applications wherecontinuous engagement and tangential drive are desired.

With the articulating handle, the tool is particularly suitable for usewhere space limitations would prevent a tool with a rigid handle fromproviding more than a few degrees of rotation. This is possible becausethe relatively short head 82 can rotate through a greater angle in agiven lateral space than a longer, rigid handle. Thus, the articulatingtool is particularly useful in spinal fusion surgery where space isquite limited.

The additional rotation provided by the articulating handle isillustrated in FIGS. 9a and 9b. In these figures, the articulating tool81 and a rigid tool 93 are each shown in use with a driven element 94 ina relatively narrow space bounded on the sides by walls 96, 97. With therigid tool, angle of rotation is limited by contact between the handleand the side walls, and the driven element is turned through an angle Aof only a few degrees of rotation as the handle moves from wall 96 towall 97. With the articulating tool, the limiting factor is the contactbetween the relatively short head 82 and the side walls, and the headtravels through an angle B which is substantially greater than the angletravelled by the longer handle in moving from wall to wall. Inapplications where the distance between the walls is greater than thelength of the head, the head can rotate through an angle of 90°-180°, ormore, while a rigid handle could move only a few degrees.

While the invention has been described with specific reference toseveral embodiments of tools for driving the operating screws of boneseparators which are utilized in spinal fusion surgery, it is notlimited to such applications, and can be employed in other applicationswhere a tangential drive and continuous engagement between the drivingtool and the driven element are desired. It is likewise not limited to aparticular type of drive gear such as a spur gear or a helical gear.Other types of gears can be employed, as can other types of tangentialdriving elements such as friction wheels and notched wheels.

Different techniques can be used to provide the tangential drive forcein place of the back and forth ratcheting action or the rotationalaction of the embodiments described. If desired, the drive gear can bereplaced with other elements such as springs or push/pull devices toprovide a tangential driving force directly to the driven element.Elements having different diameters can be used for the driving elementand the driven element to change the mechanical advantage of the drive.

The invention has a number of important features and advantages. Itprovides a simple and effective tool that is capable of continuouslyturning a driven element without disengaging the tool even though bothends of the driven device are obstructed or otherwise inaccessible. Thetool can be utilized in applications where space for manipulating a toolis severely limited as, for example, in spinal fusion surgery or incomplex mechanical or electrical assemblies. The tool is easy toposition on the driven device even when visual observation of the deviceis partially blocked. The tool requires a minimum of lateral clearancespace in order to function, and it can be manufactured economicallywithout complex production techniques.

It is apparent from the foregoing that a new and improved tool has beenprovided for driving elements which cannot be engaged from their ends.While only certain presently preferred embodiments have been describedin detail, as will be apparent to those familiar with the art, certainchanges and modifications can be made without departing from the scopeof the invention as defined by the following claims.

I claim:
 1. A continuous drive torquing apparatus for rotating a driven element about its axis, comprising a peripheral driving element adapted t be moved in a radial direction into and out of peripheral driving engagement with the driven element, a head which carries the driving element and is adapted to impart a driving torque to the driving element when swung back and forth about the axis of the driven element with the driving element in peripheral driving engagement with the driven element, an elongated handle for swinging the head back and forth about the axis of the driven element, and means pivotally connecting the elongated handle to the head for movement about an axis parallel to the axis of the driven element to permit articulation between the handle and the head as the head is swung back and forth to produce the tangential driving force with the driving element in peripheral driving engagement with the driven element.
 2. The apparatus of claim 1 wherein the driving element comprises a rotatively driven gear having peripheral teeth for engagement with the driven element.
 3. The apparatus of claim 1 wherein the head includes a pair of aligned notches for rotatively receiving a portion of the driven element and positioning the driving element a predetermined distance from the axis of the driven element with the driving element in peripheral driving engagement with the driven element.
 4. The apparatus of claim 1 wherein the head includes a ratchet which provides a driving connection with the driving element when the head is moved in one direction and permits the head to move freely in another direction without connection to the driving element.
 5. In combination: an axially extending drive screw having a pair of oppositely threaded portions and a peripherally engagable drive portion between the threaded portions, a pair of elements threadedly mounted on the threaded portions for movement toward or away from each other upon rotation of the screw, a wrench head, a driving element carried by the wrench head and adapted to be engaged from the side with the drive portion of the screw, means operatively connecting the wrench head to the driving element in such manner that back and forth movement of the head about the axis of the driven element produces a tangential driving force at the driving element, means for holding the driving element in peripheral driving engagement with the drive portion of the screw so that the tangential driving force produced by movement of the wrench head is applied to the drive portion to rotate the screw, an elongated handle for moving the wrench head back and forth about the axis of the driven element, and means pivotally connecting the elongated handle to the wrench head for movement about an axis parallel to the axis of the drive screw to permit articulation between the handle and the wrench head as the wrench head is moved back and forth to produce the tangential driving force.
 6. The apparatus of claim 5 wherein the driving element and the drive portion of the screw are gears having teeth which mesh with each other when the driving element is in driving engagement with the drive portion.
 7. The apparatus of claim 5 wherein the means for holding the driving element in peripheral driving engagement with the driving portion of the screw comprises a pair of aligned notches for rotatively receiving portions of the screw on opposite sides of the driving portion and positioning the driving element a predetermined distance from the axis of the screw.
 8. The apparatus of claim 5 wherein the means operatively connecting the wrench head to the driving element comprises a ratchet which provides a driving connection with the driving element when the head is moved in one direction and permits the head to move freely in another direction without connection to the driving element.
 9. A wrench for rotating a driven element about its axis, comprising a head, a drive gear rotatively mounted to the head and adapted for movement in a radial direction into and out of peripheral driving engagement with the rotatable element, ratchet means providing a driving connection between the head and the drive gear when the head is rotated in one direction about the axis of the driven element and permitting the head to rotate freely in the other direction with no driving connection with the gear, means for holding the drive gear in peripheral driving engagement with the driven element so the drive gear imparts a tangential driving force to the rotatable element when the head is rotated in the one direction, an elongated handle for rotating the head back and forth about the axis of the driven element, and means pivotally connecting the elongated handle to the head for movement about an axis parallel to the axis of the driven element to permit articulation between the handle and the head as the head is rotated back and forth to produce the tangential driving force with the driving element in peripheral driving engagement with the rotatable element.
 10. The wrench of claim 9 wherein the means for holding the drive gear in peripheral driving engagement with the rotatable element comprises fork means having a pair of aligned notches for rotatively receiving a portion of the rotatable element and holding the drive gear a predetermined distance from the axis of the driven element. 